Isaiah h



(No ModeL) I. H. FARNHAM.

ELEGTRIGAL CIRCUIT AND APPARATUS GUARD. No. 392,724. Patented Nov. 13, 1888.

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N. PETERS. FhnloLhhognpl-mr. Washington. In:

ISAIAH H. FARNHAM, OF MALDEN, ASSIGNOR TO THE NEW TELEPHONE AND TELEGRAPH COMPANY, OF

ELECTRSCAL. ClRCUl'l' ANY APPARATU EN GLAND BOSTON, MASSACHUSETTS.

EBPECIFICATION forming part of Letters Patent No. 392,724, dated Tovenz'ce Application filed Ju y 20, 1887. Serial No. 243,597. (No model.)

To all whom it may concern:

Be it known that I, Isnmn H. Fiinnnitn, ofMalden,in the county oflyiiddlesex and State of Massachusetts, have invented certain Improvements in Electrical Circuit and Appa ratus Guards, of which the following isaspecification.

My invention relates to the class of appli ances employed for the purpose of protecting telephonic and other electrical instruments from being destroyed or injured by the action of currents of abnormal strength which may through accident be caused to traverse a circuit in which the instruments are included.

[5 Various instruments have been devised for the purpose of accomplishing this result,and these have been arranged in some cases to establish a shunt-circuit around the instrument-helices, in others to establish an eartlrconnection irr 2o dependent of and external to the instruments to be protected, and still another class has been designed for the purpose of completely opening the main circuit, thus effectually disconnecting the instruments from the destroy- 2 ing influences.

Myinvention is an appliance which is capable of adaptation to either of the classes or modes of operation indicated, and when applied in one way-say when arranged to shunt the instruments in case of danger-it is en tirely within the range of ordinary electromechanical skill to alter the connections if either of the other modes is desired.

Designed, therefore, for the object and pur- 5 pose of protecting electrical instruments, to that end my invention consists in applying to the electro-magnet of any electrical instrument an extra armature responding only to the passage of an abnormally strong current through the magnet-coils and controlling a normally-open shunt-circuit arranged around the said magnet or around any number of instrument-s, or adapted to maintain normally the integrity of the main circuit, but to cause 5 the same to be impaired upon the passage through the magnctcoils of an unduly strong current.

It consists, also, therefore, in the combination,with such extra armature, of circuits so arranged. and adapted that when the said armature is attracted by the electronnaguet certain changes may be el'fectuated in the character of such circuits,whereby the apparatus is placed out of danger.

It further consists in a construction of the operating mechanism wherebythc said change in the said circuits is effected only in case the abnormal current has some degree of pcrmanency and whereby the continuity of the circuit through the instruments is maintained 6o unimpaired, even though the armature be momentarily attracted by a magnetic impulse due to a lightningdischarge. The circuitchanging element of my invention is thus maintained irresponsive to lightning discharges, andis not likely, therefore, when they occur, to require resetting.

XVhile I prefer to employ the electro-mag net of the apparatus to be protected or of one of the appliances to be protected, this is not absolutely necessary, and it may upon occasion be found convenient to provide an especial and additional clectro-magnet for the purpose. This, however, is not generally desira ble, as it is a disadvantage to include in the line a greater number of magnetic helices than are actually essential. In one embodimentof my invention I have applied it to a magnetoelectric bell of the class universally used in connection with telephones. The bell-magnet So is provided with the usual inductivcly-polarized centrally-pivoted armature, to which is attached the bell-hammer. The extra armature is pivoted or hung to a fixed standard by one of its ends and is provided with a retracting-sprin t is not mounted directly opposite to any magnetic core or pole-piece, but is preferably mounted so as to project across the side of the two legs of the magnet near their ends and at a point of the cores 0 Where the coiled insulated wire is interposed actually and at all times between the armature and iron core. It may be supposed thatin such aposition it is not capable of being under any circumstances attracted by the mag- 5 netism of the core. It is, however, an absolute fact that in this positiomwhile not responsive to the influence of the ordinary currents which legitimately traverse the magnctcoils, (the adjustment of the retracting-spring and zoo the position of the armature with respect to the magnet contributing to this result,) it is perfectly and promptly responsive to the pres ence of an unduly or abnormally strong current and becomes operative (although, however, such a position is in most cases preferred, it is not essential, and the armature may be mounted in any part of the magnetic field where convenient, and in that case its delicacy and responsiveness would have to be regulated by adjusting the distance of the armature from the magnet and by adjusting the tension of the retracting-spring thereof,) its free end advancing toward the magnet and eflecting the desired change in the circuit. In its normal position, in some instances, it abuts against the end of a small lever, which is provided with a spring tending to pull it forward. The lever is, however, prevented from yielding to this impulse by the interposition of the abutting armature. If the armature be removed, the small lever, which constitutes one element of a circuit-changer or circuit-closer, springs forward in obedience to the pull of the spring, and is thus permitted to effect the desired change in the circuit for purposes of protection, its change of position being caused to shunt the apparatus or to open or ground the main circuit, as may be desired. The passage of a dangerous current through the magnetcoils causes the extra magnet to be attracted, and thus removes the obstacle from the circuit-changing lever-,which is thus actuated, as described.

In the drawings illustrating this specification, Figure l is a diagram showing an electromagnet and circuit-changer separated thereby, being an illustration of my invention in its simplest form. Fig. 2 shows a more perfect form adapted to work with the electro-magnet of a magnetobell. Figs. 3 and 3 are horizontal sections of Fig. 2, partlyin diagram, showing the circuit-changer in operative as well as in non-operative position. Fig. 4 is a modification showing one way of rendering the movementof the armature sluggish, so as to be prac tieally irresponsive to lightning-discharges. Figs. 5, 6, and '7 are examples of modified apparatus, all in diagram, the circuit-changer in each case being adapted to break the circuit. Fig. Sis a plan view of an electro-magnet, showing the extra armature in a somewhat diiferent position and adapted to work directly against the side of the iron pole-pieces. Fig. 1 shows my invention reduced to its simplest form.

An electro-niagnet, m, employed primarily for another purpose-for example, to operate an electric bell, as indicated in Fig. 2-is protected from damage likely to accrue from accidental and unduly-intense currents passing through its helices by an extra-soft iron armature, d, mounted across the side of said magnet near its poles and trunnioned or pivoted at 1'. It is normally retracted against abacklimit stop, being held in position by a spring, h. Owing to its position in a comparatively feeble field of force, this armature does not respond to the ordinary and legitimate line-currents, but continues inert. \Vhen in its normal, position the free end of the extra armature abuts against the free end of a hinged or pivoted lever, c, holding it against the power of a spring, is, away from a contact-stop,j. The main line entering at L passes through the electro-magnet m and through one or more other electro'mag11ets,9, if desired, passing out by the wire Z. From a point, at, of the circuit, on one side of the apparatus to be protected, one side, 0, of a shunt-circuit extends to the front contact'stop, j, of the circuit changing lever c. From a point, 5, on the other side of said apparatus the other side, 1), of the shunt-circuitextends to the said circuitchanging lever. As long as the working currents only traverse the magnet-coils, the circuit-changer remains quiescent. W'hen, however, the current passing through the helices of the magnet in approaches a dangerous intensity, (owing, for instance, to a cross with an electric-light circuit,) the armature d is attracted, and the circuit-changing lever 0 thereby released makes contact with the stop j, thus short-eircuiting the apparatus and protecting it from injury.

If it be desired to ground the circuit for the purpose of allowing an escape of the electricity to earth, this may "readily be accomplished by adding a second contact stop,j, connected with a ground-wire, as indicated in dotted lines. By adopting this feature not only is the apparatus short-circuited, but the circuit is grounded on both sides of said apparatus.

In Figs. 2, 3, and 3" the protecting appliance is adapted to be operated by the electromagnet of a magneto-electric bell, and it is furthermore arranged in such a way as to be irresponsive to sudden discharges or instantaneous currents-such as lightning-against which special arresters or protectors have been provided. L is the incoming and Z the outgoing line or the ground end. The electro-magnet m. is included in the said line circuit and mounted mechanically in a suitable frame, f, whereon also the bells b are mounted. The bellhaminer is attached to and is operated by the ordinary centrally-pivoted armature, a. The extra armature d is pivoted orswiveled at 9- to a bracket, 0, fastened to one side of the frame, and, normally yielding to the pull of its retracting-spring h,is retracted against its baclu stop The circuitchanging lever c is pivoted at u, and is pulled forward by the spring 7t until it abuts against the free end of the armature (1, when said lever is in its normal position. The said free end of the armature (Z is beveled off, as shown, and the end of the circuit-changing lever is provided with an angular lip, which engages with and projects over the beveled end of the armature, for a purpose which will hereinafter appear. A shuntcircuit is arranged as in Fig. 1,0ne side thereof leaving the line L at the point-1 and extending ICC to the front contact-stop, j,of the circuit-changing lever c, and the other side leaving the line Z at the point 5 and uniting with the lever itself. 8 and 9 are additional apparatus included in the portion of the main circuit to be protected by the shunt. As in the preceding case, the regular currents of the line do not affect the additional armature. The appliance shown in Fig. 1 is, however, responsive to short and quick discharges or currents of electricity such as lightning-whieh is in many cases undesirable. To prevent this, I have shaped the armature and lever ends as in Figs. 3 and 3 and have arranged their engagement in the manner shown. Upon the occurrence of such a sudden discharge should the magnet m becomesufficientl y energized to actuate the armature d the said armature will make a quick movement forward. The sudden forward motion will by means ofthe overlapping of the lip of the leverc impart an impulse to the said lever, causing it to fly momentarily back into the position 0, (shown in dotted linesin Fig. 3,) and before the said lever can recover itself the armature (Z has resumed its normal position. The eircuitchanger is thus prevented from being actuated by sudden and extremely brief impulses of electricity. If, however, the abnormal current be steady, the armature (Z, when once attracted, will be held forward for a period of time sufiiciently long for the lever c to pass under it and to make contact with the i'ront stop, j, closing the shunt -circuit. In Fig. at the same elements are utilized with the exception of the device for preventing the appliance from being operated by lightning. In this case, instead of modifying the engagement of the armature and circuit changing lever and causing the front stroke of the former to kick the latter backward, I provide the armature (1 with a piston, 1', working in adash-pot, s, filled with some thick or viseid fluid, and the armature, being thus rendered sluggish, will be prevented from responding to an impulse of electricity as brief as that of a lighthing-discharge.

Fig. 5 shows an appliance substantially identical in construction with Fig. 1, but differing in the electrical connections. In the present case the armature d when attracted acts to open the circuit instead of shunting the apparatus. The line-circuit L entering connects with a contact-spring, a, mounted on a base, o. The outgoing line Z, after passing through the electro-magnet m, continues by wire to the lever c, to which it is connected. The lever c and spring a are normally in electrical connection, being held together by the end of the armature (1 when not in action. \Vhen the said armature is attracted, the lever and spring part company and the circuit is opened.

Fig. 6 is modification, which, like Fig. 5, opens the circuit upon the passage of an abnormal eurrent through the coils, but which is made irresponsive to lightning by adopting the construct-ion at the armature and lever ends shown and described in connection with Figs. 3 and 3".

In Fig. 7 a further modificationisillustrated, in which the lever 0, when struck backward into the dotted-line position 20, is, as before, caught on the armature end if the impulse of electricity actuating the said armature be brief; but if the attraction of the said armature continue until the end of the lever 0 can swing past it to the dotted position no shown the link of spiral conductor held by thehook 0 will be detached therefrom and the circuit thereb opened.

Of course, though I have for convenience of illustration shown a magneto-bell as being the form of apparatus to be protected, and have described the attachment of this protector to and in combination with the magnet of such a bell, it is evident that it will work with equal efficiency in association with and in combination with the electro-magnet of any other elec tro-magnetic appliance or instrument.

Ashereinbefore stated, it is not an essential feature of my invention to mount the actuating-armature of the protector in a position where the coils of wire surrounding the magnet-cores are interposed between it and the said cores; and Fig. 5 exhibits an alternate construction wherein the armature (Z is mounted at the side of the poles of said cores, its re spousiveness being regulated by the distance at which it is mounted therefrom and by the strength of the counter-force exerted by the retracting spring 3.

I clain1- 1. The combination, substantially as herebefore described, of an electric circuit, an elec tric instrument included therein, a normally-- open shunt of said circuit round the magnet of said instrument, a circuit-eloser controlling the terminals of said shunt-circuit, an auxiliary armature controlled by an electromagnet included in the main circuit and normally in terposcd in the path of said circnit-eloscr and thereby preventing its operation, but releasing the same when attracted, and a retarding device to prevent the circuit-closer from aeting when released by a momentary and noncontinuous attraction of said armature, for the purposes specified.

2. The combination, substantially as hereinbefore described, of an electric circuit or main-line conductor, an electromagnetic instrument or apparatus included therein, an extra or auxiliary armature mounted, as described herein, at the side of the electro-magnet of said apparatus, but retracted therefrom and adapted to be attracted thereto only upon the passage of abnormally strong currents, a circuit-changer consisting of a pivoted lever and a contact-point therefor, the said lever being normally held away from the said contact-point by the interposition of the said extra armature when (1 uiescent, a normally open derived circuit of the main line round the instrument to be protected, the said de rived circuit being controlled by the said eir cult-changer and adapted to be closed by the attraction of the extra armature and the consequent release of the pivoted lever of the circuit-changer, and a retarding device whereby the said circuit-changer is prevented from closing the said shuntcircuit on the occurrence of a powerful but brief electrical i1npulse or current, while allowed to act when the said impulse or current is sustained.

3. In a protector of electrical apparatus, the combination, with the electro-magnet of an instrument in a main-line circuit, of a norn1ally-open shunt-circuit of said main line, adapted when closed to shunt the said magnet, an automatic circuit-changer controlling the said shunt-circuit and included therein, an extra armature controlling the said circuitchanger and adjusted to be actuated by said electromagnet only when the said magnetis energized by an abnormally strong current, and a retarding device for the said circuit-changer, whereby it is rendered irresponsive to extremely brief discharges or currents, such as lightning discharges, substantially as described, and for the purposes specified.

4. The combination, in an electrical-instrument protector, of a main line, an electrical instrument or apparatus, an independent or auxiliary armature mounted in proximity to the electro-magnet of said electrical instrument, so as to be attracted thereby upon the passage of an abnormal current, and a circuitchanger connected with and controlling the said main circuit and itself controlled by the said extra armature and maintained inert, while the said armature remains unattracted but released and allowed to become operative upon the attraction of said armature under the influence of a dangerous current, substantially as described.

5. In combination with the electro magnet of a magneto-bell or other electric instrument, a protecting appliance therefor comprising a circuit-changer consisting of a pivoted contact-lever having at its free end an angular detent or projecting piece, a contact-point serving as a front stop therefor, and a spring exerting a constant force upon the said contactlever and tending to draw the same against the said contact-point, a normally-open shunt or loop of the electro-magnet main circuit arranged around the said electro-magnet, comprising an electrical connection from a point on the main circuit on one side of the said magnet to the circuit-changer contact-point and a second connection from a point on the main line on the other side of the electro-mag net to the contact-lever, and means, as indicated, for normally maintaining the shuntcircuit open, for closing the same upon the passage through the magnet of a continuous current, and for preventing the same from closing upon a lightningdischarge or other impulse of brief duration, said means consisting of an extra or auxiliary armature mounted opposite to the side of the said magnet, near the poles thereof, in such a manner as to respond only to the passage of abnormally heavy currents, the second armature being normally retracted and constituting an obstacle interposed in the path of the circuit-changing lever and provided with a beveled end engaging behind the angular projecting piece thereof, all substantially as described, and adapted to operate as and for the purposes specified.

6. The electro-magnet m, the armature (Z, beveled at its free end and mounted across the helices thereof, so as to be responsive only to abnormally strong currents passing through the said helices, and the circuit-closing lever 0, having an angular projection normally rest ing in front of the beveled end of the said armature end and being retained thereby from its point of rest,the contactpoint j therefor, constituting said point of rest, the said lever and contact-point being terminals of a normally open circuit, all in combination, whereby the armature, when attracted, is adapted to act, first, to kick the lever cl to a greater distance from its contact-point for the purpose of preventing it from reaching its cont-actpoint ifthe attraction of the armature be but momentary, substantially as specified.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this letth day of July, 1887.

' ISAIAH H. FARNHAM.

Vfitnesses:

V. M. BnnTnoLD, Gno. WILLIs PIERCE. 

